JPS6241725A - Production of lens of refractive index distribution type - Google Patents

Abstract

PURPOSE:To produce lens of refractive index distribution type simply in a short time, by diffusing heterogeneously a metallic ion having high electron polarizability into part of the surface of porous gel obtained by hydrolyzing a metallic alkoxide and heat-treating the gel at high temperature. CONSTITUTION:A metallic alkoxide such as Si(OCH3)4, etc., is hydrolyzed to give the flat porous gel 2'. This porous gel 2' is used as a base material, optionally heat-treated to give porous glass, which is provided with the mask 4 having the diffusion holes 5 at a lens-forming part. Then, in the diffusion holes 5, a solution of metallic ion having high electron polarizability, such as Tl, Cs, etc., is brought into contact with the gel 2'. Properly the contact time is usually about 0.5-5hr. Consequently, the diffusion layer 3 of the metallic ion is formed, the gel 2' is heat-treated at about 1,100-1,300 deg.C and the non-porous glass layer 2 is made to give the lens 1 of refractive index distribution type.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a method for manufacturing a gradient index lens. More specifically, the present invention relates to a method for manufacturing a gradient index lens useful in various fields such as light guides, peripheral light elements for optical communication systems, optical systems for optical analyzers and copying machines.

(B) Conventional technology A so-called gradient index lens, which imparts a lens effect by changing the refractive index in a transparent medium, can impart a lens effect in a flat plate shape, compared to ordinary optical lenses.
It has various advantages such as being able to form an image on the end face, being able to freely select the imaging characteristics, and being easily formed into an array or matrix of lenses, and has recently been attracting attention in the field of optical communications.

Among these, graded index lenses using glass materials usually involve (1) bringing a part of the glass substrate into contact with a predetermined molten salt to perform ion exchange through diffusion, which results in metal ions with high electronic polarizability (e.g. There is a method (ion exchange method) in which the refractive index is changed by nonuniformly distributing thallium or cesium) in the glass substrate; A solution of a metal element is brought into contact with a part of the metal element to impregnate it and form a concentration distribution.
It is then produced using a method (Molecular Stuff Ink Method) in which it is converted into a transparent glass body by drying, high-temperature heat treatment, etc. Lenses obtained using the ion exchange method are known as Selfoc lenses. .

(c) Problems to be solved by the invention However, in the above ion exchange method (iv), it takes an extremely long time for ion diffusion and exchange (for example, immersing a masked glass substrate in molten salt for several days); Even if it was carried out for a long time, there was a limit to ion diffusion, and at most only one lens with a diameter of about 5 mm could be formed. On the other hand, in the molecular stuffing method, making the glass substrate porous is complicated and takes a long time (for example, it takes 2 days for phase separation treatment and 20 days for acid treatment).Moreover, the mounting process is complicated and special equipment is required. There was a problem that required .

This invention was made in view of the above situation, and it is possible to obtain a gradient index lens particularly easily and in a short time.
Moreover, it is an object of the present invention to provide a manufacturing method that can easily increase the lens aperture.

(d) Means and operation for solving the problems Thus, according to the present invention, j
A solution of metal ions with high electronic polarizability is brought into contact with a part of the surface of the porous gel for a predetermined period of time to diffuse the metal ions unevenly into the porous gel, and then this porous gel is Provided is a method for manufacturing a refractive index F-type lens, which is characterized by subjecting it to high-temperature heat treatment to form a gradient index lens.

This invention uses a so-called porous gel obtained by hydrolysis, which is an intermediate gel produced during glass manufacturing using a metal alkoxide solution method, as a base material, and metal ions with high electronic polarizability are added to this gel in a solution state. The fact that this metal ion diffuses and exchanges ions within the porous gel in an extremely short time when brought into contact with it, and the non-porous oxide glass that is sintered with this metal ion corresponds to the diffusion part and exhibits a lens effect. Based on facts.

Porous gels from metal alkoxides can be obtained relatively easily by hydrolysis, and furthermore, diffusion and ion exchange can be carried out rapidly as described above. Therefore, according to the method of the present invention, a desired gradient index lens can be obtained simply and in a short time.

As the metal alkoxide used in this invention, lower alkoxy metals are suitable, and Si (OCH3)4S!
(OC2H5)4, AQ (OC3Hy)3, T!
(OC3H7) 4, Na OCH3
, B(OCzfgo5)3, etc., and among these, lower alkoxysilanes are preferably used.

The porous gel used in this invention is obtained by subjecting a solution of the metal alkoxide to hydrolysis conditions, and usually
It is obtained by dissolving a metal alkoxide in a water-containing hydrophilic organic solvent, adding a small amount of acid as a hydrolysis accelerator, and subjecting it to drying conditions at mild temperatures to promote hydrolysis and volatilization of the solvent. As the water-containing hydrophilic organic solvent, it is appropriate to use a volatile organic solvent containing water such as water-containing methanol and water-containing ethanol. In addition, mineral acids such as hydrochloric acid, nitric acid, and hydrofluoric acid are suitable as acids to be added in small amounts.
It is sufficient to add a small amount so that the pH of the solution is adjusted to about 2 to 5. Drying conditions may be natural drying, but usually 5
It is preferable to carry out the heating gradually at a temperature of about 0 to 80°C from the viewpoint of uniformity of the gel obtained.

By controlling the drying conditions, a desired porous gel can usually be obtained in 150 to 240 hours.

The porous gel is then contacted with a solution of highly electronically polarizable metal ions, usually by immersion in the solution. At this time, as in the conventional ion exchange method, it is necessary to perform appropriate masking on the surface of the porous gel so that the solution comes into spot contact only in the vicinity of the center of the intended lens formation site. Such masking is typically performed with metal vapor deposition. By forming a large number of such contact spots in one porous gel, it is possible to easily obtain a gradient index lens in the form of a rear array or matrix.

Although thallium ions and cesium ions are suitable as the above-mentioned metal ions having large electronic polarizabilities, other ions having similar electronic polarizabilities are also applicable. As these solutions, it is suitable to use solutions of easily soluble salts of this metal ion, and they are usually used in the form of an aqueous solution. Note that the solution at the time of contact may be at room temperature, but it is preferable to contact in a heated state from the viewpoint of rapid diffusion and exchange of metal ions. -F metal ions enter and diffuse into the porous gel from the parts that come into contact with this solution, and there, they are partially ion-exchanged with hydrogen atoms in the hydroxyl groups of the metal hydroxides that make up the porous gel. A non-uniform diffusion layer of metal ions with the intended concentration gradient will rapidly form around the contact site. At this time, the spread of the diffusion layer can be controlled by adjusting the contact time, and the contact may be carried out for a predetermined time so as to obtain the intended lens aperture. Normally, contact for about 0.2 to 5 hours is sufficient, but by contacting for an even longer period of time, it is possible to easily produce lenses that exceed the aperture limit of conventional SELFOC lenses.

As described above, by subjecting a porous gel having a non-uniform diffusion layer of metal ions to high-temperature heat treatment, the gel including the diffusion layer is converted into a non-porous oxide glass, and a desired gradient index lens can be obtained. That will happen. The high temperature heat treatment at this time is usually carried out at a high temperature of 1100 to 1300°C for about 2 to 10 hours, and from the viewpoint of homogeneity, it is preferable to carry out the treatment by gradually increasing the temperature to the above temperature. Before the contact treatment with metal ions having a large electronic polarizability, the porous gel of the substrate is previously heat-treated to convert it into porous glass, and then treated in the same manner as above, which results in a higher It is also possible to easily manufacture a gradient index lens. Therefore, this invention heat-treats a porous gel obtained by hydrolysis of a metal alkoxide to form a porous glass, and then uses this as a substrate and contacts a part of its surface with a solution of metal ions having high electronic polarizability for a predetermined period of time. The present invention also provides a method for manufacturing a gradient index lens, characterized in that the metal ions are diffused non-uniformly into porous glass, and then the porous glass is heat-treated at a high temperature to obtain a gradient index lens. It is something to do. At this time, the conversion of porous gel to porous glass takes place at a temperature of 200 to 800°C.
It is appropriate to do this for about an hour. If it exceeds 20 hours, the porosity will be lost and the diffusion of metal ions will be inhibited, which is not preferable.

Note that the shape of the porous gel or porous glass may be arbitrarily determined depending on the application, but for example, using a cylindrical body,
By adjusting the refractive index so that it changes in the radial direction by approximating a square distribution, it is possible to easily obtain a product equivalent to a conventional SELFOC lens.

(e) Actual flow example Example 1 Ethyl silicate s i (OC2t-1s > 4 1
00zf, ethanol 5011, water 100x! and hydrochloric acid 1011 were mixed and refluxed at 80° C. for 2 hours to obtain a uniform solution of ethyl silicate. This solution was placed in a polystyrene container (60 x 55 x 10 mm), and five pores with a diameter of 1 mm were made in the upper part of the container and kept at 70°C to gradually hydrolyze the ethyl silicate and dry it for 7 days. later 2
A 5 x 22 x 6 mm flat plate of dried porous gel was prepared in one piece.

By depositing aluminum on the surface of this flat gel, six diffusion holes with a diameter of 0.5 mm were created at a pitch of 5 mm.
[A mask for IJIH is formed as shown in Figure 1, and this surface is coated with an aqueous thallium nitrate solution (TρNO310 (+/100% water).
ffZ> for 0.5 hours at 100°C to diffuse thallium ions into the gel through the six pores to form an ion-exchange porous gel. (4) is a mask with diffusion holes (51). It shows.

The mask was then removed by fluorine etching and
℃ for 1 day, heated to 600℃ at 50℃/hour, held at 600℃ for 5 hours, further heated to 900℃ at 50℃/hour, and heated to 1100℃ at 50℃/hour in helium atmosphere. By heating the lower part of the back at a high temperature, the porous gel was converted into a non-porous oxide glass, and a gradient index flat lens (1) of the present invention as shown in FIG. 2 was obtained. In the figure, (2) shows a non-porous glass layer, and (3) shows a diffusion layer of thallium element.

This flat lens has good transparency and exhibits a plano-convex lens action with a lens diameter of approximately 1.3 mm in the six diffusion layer portions.

Example 2 A porous gel made of a hydrolyzate of ethyl silicate prepared in the same manner as in Example 1 was previously heat-treated to convert it into porous glass. This heat treatment was carried out by raising the temperature to 600°C at a rate of 50°C/hour and holding it at 600°C for 5 hours.

Using the flat porous glass obtained in this way as a substrate, a mask was formed on this surface in the same manner as in Example 1,
Thallium nitrate aqueous solution (TQNo.

The glass was soaked in 10 g/100 yf of water at 100° C. for 1 hour to diffuse Kurilam ions into the porous glass through each diffusion hole.

Next, this porous glass was heat-treated under the same heating conditions as in Example 1 to sinter it and make it non-porous, thereby obtaining a flat lens similar to that shown in FIG. 2. The characteristics of this plane lens are good as in Example 1, and the lens diameter is approximately 1.1 m.
It was 1 Tl.

(e) Effects of the Invention According to the method of the invention, metal ions having a large electronic polarizability can be rapidly diffused, and the substrate can also be produced relatively easily. Therefore, compared to the conventional ion exchange method or the Molecki Collar Stuff Ink method, handling is simpler and a desired graded index lens can be obtained in a shorter time. When a porous gel is used as a substrate, it is extremely advantageous because metal ions can be rapidly diffused and no preheating treatment is particularly required.

Furthermore, since diffusion can be performed in a short time, it is also possible to manufacture lenses with larger diameters than conventional ones.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one step of the method for producing a gradient index lens according to the present invention, and FIG. 2 is an explanatory diagram showing an example of the structure of a gradient index flat lens obtained by the method of the invention. be. (1)・・・Gradient index flat lens, (2)・
... Non-porous glass layer, (3) ... Diffusion layer of thallium element, (4) ...
...Mask, (5) ...Diffusion hole. Figure 1

Claims (1)

[Claims] 1. A porous gel obtained by hydrolysis of a metal alkoxide is used as a base, and a part of the surface of the gel is brought into contact with a solution of metal ions having a high electronic polarizability for a predetermined period of time to make the metal ions porous. 1. A method for producing a gradient index lens, which comprises unevenly diffusing the porous gel into a gel, and then subjecting the porous gel to high temperature heat treatment to obtain a gradient index lens. 2. The manufacturing method according to claim 1, wherein the metal ion having a large electronic polarizability is thallium or cesium ion. 3. A porous gel obtained by hydrolysis of a metal alkoxide is heat-treated to form porous glass, and a part of the surface of the glass is brought into contact with a solution of metal ions having a high electronic polarizability for a predetermined period of time to remove the metal ions. 1. A method for producing a gradient index lens, which comprises non-uniformly diffusing the porous glass into a porous glass, and then subjecting the porous glass to a high temperature heat treatment to obtain a gradient index lens. 4. The manufacturing method according to claim 3, wherein the metal ion having a large electronic polarizability is thallium or cesium ion.